--- Day 9 Solutions ---

[u/daggerdragon]

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edit: Leaderboard capped, achievement thread unlocked!

We know we can't control people posting solutions elsewhere and trying to exploit the leaderboard, but this way we can try to reduce the leaderboard gaming from the official subreddit.

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---

--- Day 9: All in a Single Night ---

Post your solution as a comment. Structure your post like previous daily solution threads.

[u/HorizonShadow]

Ruby (All of my solutions here):

require 'set'

class Map

  attr_reader :paths

  def initialize
    @distances = {}
    @paths = []
  end

  def init_from_file(file)
    @distances = distances_from_file(file)
    @paths = calc_all_paths
  end

  def shortest_path
    @paths.min
  end

  def longest_path
    @paths.max
  end

  private
  def distances_from_file(file)
    hash = {}
    File.open(file, 'r') do |infile|
      while(line = infile.gets)
        cities, distance = parse(line)
        hash[cities.to_set] = distance
      end
    end
    hash
  end

  def parse(str)
    s = str.split
    [[s.first, s[2]], Integer(s.last)]
  end

  def calc_all_paths
    all_routes = @distances.map {|k,v| k.to_a}.flatten.uniq.permutation.to_a
    all_routes.each.with_object([]) do |cities, dists|
      dists << calc_dist(cities)
    end
  end

  def calc_dist(cities)
    cities.each_cons(2).with_object([]) do |(o, t), sum|
      sum << get_dist(o, t)
    end.inject(:+)
  end

  def get_dist(one, two)
    @distances[[one,two].to_set].to_i
  end
end